High speed contacting device



March 2, 1965 E. J. DIEBOLD 3,172,010

i HIGH SPEED CONTACTING DEVICE Original Filed Jan. l0, 1956 7 Sheets-Sheet l r E. Z

7/4b Y Z0 E''E: ZA

March 2, 1965 E. J. Dil-:BOLD 3,172,010

HIGH SPEED CONTACTING DEVICE Original Filed Jan. 10, 1956 '7 Sheets-Sheet 2 EE- 5. EE-5. 5.

March 2, 1965 E. J. DIEBOLD 3,172,010

HIGH SPEED coNTAcTING DEVICE Original Filed Jan. 10, 1956 7 Sheets-Sheet 3 March 2, 1965 E. J. DIEBOLD 3,172,010

HIGH SPEED CONTACTING DEVICE Original Filed Jan. l0. 1956 7 Sheets-Sheet 4 fan/zen JMA/.wwwa E5- Z. BY

srfa Ems, Erase, 6eme Jafar/v March 2,l 1965 E. J. Dlt-:BOLD 3,172,010

HIGH SPEED CONTACTING DEVICE Original Filed Jan. l0.v 1956 '7 Sheets-Sheet 5 l Z/da, X" EE-:15. 55.15A-

.Zay

March 2, 1965 E. J. D11-:BOLD 3,172,010

HIGH SPEED CONTACTING DEVICE Original Filed Jan. 10, 1956 'T Sheets-Sheet 6 BY dire@ Enne, 5465/?, Qffe gJbFFf/v March 2, 1965 E. J. DIEBOLD HIGH SPEED coNTAcTING DEVICE Original Filed Jan. 10, 1956 7 Sheets-Sheet 7 United States Patent 3,172,010 HIGH SPEED CONTACTING DEVICE Edward John Diebold, Palos Verdes Estates, Calif., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Original application Jan. 10, 1956, Ser. No. 558,349, now Patent No. 2,951,188, dated Aug. 30, 1960. Divided and this application Mar. 4, 1960, Ser. No. 12,764

5 Claims. (Cl. 317-11) My invention relates to a synchronous circuit breaker and is a divisional application of my co-pending application Serial No. 558,349, tiled January 10, 1956, now Patent Number 2,951,188, granted August 30, 1960, and assigned to the assignee of the present application.

In the past, an attempt has been made to utilize the repulsive or attractive interaction between two current carrying coils to effect the motion of a movable contact of a contact device. These previous attempts, however, have proven to be unsuccessful since a separate contact and two individual coils were used whereby one of the coils was attached to the movable contact and upon energization of the second coil the entire movable contact and coil had to be accelerated to achieve circuit interruption. It is to be realized, however, that this prior concept required the acceleration of a relatively high mass of both a coil and a movable contact. In view of this relatively high mass, the forces required to achieve a given acceleration become prohibitively high, too high for any known material to withstand. This -limits the possible acceleration to a low value, which limits the value of the device. Besides the material limitation, there is also the necessity of accelerating a large mass which requires a prohibitively large amount of electrical power for the energization of the activating coil.

In accordance with the principles of my novel invention, I overcome this relatively high movable mass which must be accelerated by providing a unitary structure for both the movable contact and the electrical winding which accelerates this movable contact to a predetermined contact position responsive to the energization of an operating means, such as another Winding.

More specifically, the movable contact which may be a ring-shaped conductor can make contact with stationary conductors along the surface of a cone and a circuit is opened or closed at the contact surfaces. The ringl shaped movable contact is further positioned to be closely situated to an operating winding so as to obtain good coupling between the oper-ating winding and the winding formed by the ring shapeof the movable contact and the operating winding is energizable by a strong current of very high frequency.

If now the primary winding is energized, as by means of the discharge of a capacitor, an extremely high current of ropposite direction and same frequency will be induced in the ring-shaped contact. A repelling force is then existent between the coils which increases with the square of the current flowing therethrough. Since, however, this force is needed for only a very short time, an exceedingly high current is permissible because of the short time it ilows in which coil heating takes place.

In View of the extremely high permissible current, tremendous forces come into play in accelerating the movable contact with respect tothe stationary contacts. Because of the unitary structure of winding and contact, such as a solid ring of metal, the tremendous forces do not require any means of transmission of force, i.e., no movable structural parts are needed. Hence, no limits are encountered due to the limited strength of the materials which are being used.

Because of this tremendous acceleration imparted to the movable contact, the instantaneous break-down voltv turn has a dimension of the same order of magnitude or. v

as that in the operating winding.

3,172,010 Patented Mar. 21965 age between the movable contact and its cooperating contact will always be greater than the instantaneous' recovery voltage that appears across these separating This effect may be enhance by operating my' greater than the recovery Voltage thereacross,.an are` will not be formedV and arc extinguishing means need not be provided.

In the event of the formation of an arc, if the contacts are separated slightly prior to a zero current value, the magnetic field in the region of the arc will be in such a direction as to cause the arc to rotate rapidly around the vertical axis of the 'coils'. Hence, the arc is burning on relatively cool electrodes and upon passage lof the current through zero, the arc will extinguish.

I have found that due to the inherently low coupling between the operating winding and the movable winding, that the eiciency of my novel system is low. This may be appreciably increased, however, by providing a ferrite core to extend through the two coils and appreciably increase the eciency of the system.

Accordingly, it is a primarly object of my invention to prove a high speed contacting device wherein the acceleration imparted to Ia movable contact is such that the instantaneous break-down voltage between separating contacts is always greater than the instantaneous recovery voltage across the separating contacts.

Another object of my invention is to provide a mova-I ble contact for a high speed contacting device whichA the magnetic field of the relatively stationary winding to l move the movable contact towards a new position.

Still another object of my invention is to provide a high speed contacting device wherein a unitary movable contact and short circuited winding inter-acts` with any operating winding whereby energization of the operating Winding effects motion of the movable contact and, the complete system operates under a high pressure gas to thereby increase the dielectric constant between the separating contacts.

-The operating Winding of my novel invention may be formed of a conductor which is relatively thin and wound' in the form of a spiral or pancake in which the height ofthe conductor is substantially larger than its radial diameter. If now a capacitor discharge is used for energization of the operating winding, it is to be realized that this discharge will be of an extremely high frequency.

The novel movable contact of my invention may be constructed in a similar way which, by way of example, could be a single turn or ring in which the height of the greater than the radial diameter vof the turn. When a high frequency current is induced in this movable contact due to a current in the operating winding, it is under-l stood .that this current will be of the same high lfrequency In view of this exthis coupling '.distance.

v Acc'ordilg'l'y, another` objectofmy inventiony is to construct" at least one of'the operating windings or the movablowinding oflmy novel high speed contact device in sucli-"amanner that proximity effects will be brought into playto thereby increase the couplingbetweenthe coils. c

`Another` object vof my invention isl to provide an operatingwinding .which is formed of a spiral winding whereinthe height vofthe conductor usedis` substantially larger thanlits radial diameter to thereby .introduce an :appreciably large 'proximity effect due to the high frequency discharge of langenergizing capacitor.

AStill another object of my invention is to form both the operatingwinding'andthe movable Contact of my novel 'high speedcontactfdevice in such a manner that the height of the conductors forming these windings is substantially comparable to or greater than the radial diameter of the conductors, whereby proximity effect is brought into playy to increase the coupling between the operating winding and the movable Contact.

After contact separation, the movable Contact is moving ywith considerable momentum, and it must bebraked toak stop and either; maintained `in a disengaged position or be'l allowed. to returnto the contact engaged position. For this purposelprovideua novel braking cylinder or chamber which hasaninternal cross-,sectional configurationwhich will receive the shape ofthe movable Contact ri` ng. k Hence, the contact ring, which may be guided into thefcylinder. by means Aof a post extending through its center,`will,upon .entering thecylinder begin to compress theair between the ringsand the opposite .end of the cylinder which isenclosed. As the air within the cylinder is 'compressedl byv'the motion of the Contact ring therein, itjis seenfthatia force is developedwhich is in a direction `to, oppose -the motion of the lring.

Firthermore, if the contacting ydevice is operating under ahighgSp-ressure in order to achieve a high dielectric ,constan-t between the separating contacts, it is Vclear'that this opposing force willV befgreatly increased.

When fthey kineticv energy of the movable contact is finally completely transferred to compress the air between thehnlovable contact and the `enclosed end of the cylinder, itfisto beyrealized that a force will now -be exerted by compressed air to accelerate the Ymoya-ble Contact in the opposite direction.

In order to prevent this rebound of the movable contact, I .provide anannular depression in `the cylinder wall whichuisso disposed ,that uponpassagefof the movable contact'baportwill be available to allow the escape of the'cornp-ressed airbetween lthe movable contact and the end ofthecylinder wall. After so relieving the compressedair captured between the movable Contact and the end of the cylinder, the contact may be latched in a disengagedposition r, if desired, the contact may be allowed to return` to its engaged positionunder the effect cfm biasingl force, such as gravity or a spring means.

Accordingly, another object of my invention is tol provide ,a braking means for dissipating the kinetic energy of'gth" inovabl'e'contact Iafter ithas moved toward a contt disengaeed'positiom "Another object oflmy invention is to provide a guide whichhextends through thecenterof the movable contact ringV for guiding its motion between a contact engaged and contact disengaged position.

Another object of my invention is to provide a braking means for the novel movable contact of my invention which is comprised of a cylinder having an enclosed end and a cross-sectional area of a shape which will cooperate with the cross-sectional area of the movable contact.

Another kobject of my invention is to brake the motion 'of a movable contact by bringing it into an enclosed cylinder and allowing it `to compress the air between, the enclosed end of the cylinder and the contact ring itself whereby forces due to the pressure of the compressed air tend to retard the motion of the contact ring.

Anotherobject of my inventionis to guide the movable Contact into a cylinder having an enclosed end and an annular recess in the interior thereof whereby compressed.

air between the enclosed end of the cylinder an-d the contact ring itself is allowed to escape when the contact passes this annular recess.

It has been described above that the motion of the movable contact may be braked and the movable contact is thereafter allowed to return to its former position after Contact disengagement has taken place between lthe movable contact and its cooperable contact. If this is the case and it is desirable to prevent contact engagemenhit is possible to move the cooperating contact, which may be a pair of relatively stationary bridging contacts, to a remote position responsive to movement of the movable contact to a disengaged position.

This withdrawal or movement of the stationary contacts to a remote position after contact disengagement may in fact be necessary to defeat a second contact engagement in case reclosing of the circuit is to be avoided. In an actual structure, it can be realized that the stationary contacts are biased into engagement with the movable contact to obtain high contact pressure. This biasing maybe accomplished by a spring means or any other desired means. However, upon disengagement of the contacts, a rather high force would have to be brought into play in order to reengage the cooperating contact by overcoming the biasing means of the relatively stationary contacts.

The withdrawal of the stationary contacts has the advantage of makingthe circuit breaker trip free, i.e., then the circuit breaker opens under the action of the movable contact being expelled violently, the stationaryV contacts are thereafterv retracted, leaving the circuit breakeropen when the movable contact assumes .the

closed position again. Closing of the circuit breaker is effected by pushing the stationary contactsadjacent the movable7 contact. When closing Vagainst a fault, the movable contact can be expelled without delay.

vThis withdrawaly of the stationary contacts may be accomplished by various types of hydraulic or electromagnetic means which are energized responsiveto the motion ofthe movable contact or, if desired,'responsive` to the means which energizes the operatingwinding.

'Still another manner in which withdrawal of the stationary contacts may be effected is by the utilization of the compressed air in the breaking cylinder of the movable contact.

Accordingly, an important object of my invention is to provide means whereby the contact cooperating with the movable. contact is so constructed that it may be` electromagnetic means responsive to contact disengagement.

It has ybeen seen that lmy novel highV speed,A contact device can successfully interrupt circuits which may have extremely high short circuit capacities and very high rates of recovery voltage becauser the cooperating contacts separate so fast that the instantaneous breakdown voltage is always higher than the instantaneous recovery voltage.

Clearly, it is desirable to reduce the rate of rise of recovery voltage if possible, and this is possible by connecting a capacitor across the contacts. By a further extension of this idea to the casein which a pair of stationary contacts are utilized and the movable contact ring comes into bridging contact engagement therewith, I have found that by connecting a center tapped capacitor in series with the stationary contacts and connecting the center tap to the movable contact, I obtain an equal distribution of the recovery voltage across the two breaks of the contact device, reduce the rate of rise of recovery voltage and also partially eliminate the high frequency oscillations causing the extremely high recovery rates.

Accordingly, a still further object of my invention is l to utilize a center tapped condenser in conjunction with a contacting device constructed in accordance with my novel principle in which a pair of stationary contacts are utilized for bridging contact cooperation with a movable contact ring wherein the outer ends of the condenser are connected in series with the stationary contacts and the center tap of the condenser is connected to the movable contact to thereby decrease the rate of rise of recovery voltage, equally distribute the recovery voltage across the two breaks and partially eliminate the high frequency oscillations which cause high rate of rise of recovery voltage.

When utilizing an operating winding which is energized by the discharge of a capacitor, it is desirable to have this energization take place for a subsequent contact disengagement immediately prior to a zero current value in the circuit being protected. This is extremely desirable, first, because the interrupting duty on the disengaging contacts is decreased and, secondly, any arc which is formed will extinguish when the current subsequently passes through the zero current value. This is particularly true in the case of my novel device since the arc will move extremely rapidly around the axis of the movable contact and will be in contact with this relatively cool body.

I, therefore, provide a novel trip circuit which is effective to connect a charged capacitor to the operating coil a time immediately prior to an instantaneous zero current value rregardless of the current value at which the fault occurs on the circuit. That is to say, if the fault occurs during a relatively high instantaneous current value, the trip is delayed until this current value, in the case of an A.C. circuit, decreases to substantially zero value. Obviously, this same principle may be utilized for a reverse current trip in the case of a D.C. circuit.

More specifically, I provide a trip circuit in which the line current is measured with a current transformer and the output of the current transformer is connected to a saturable reactor which in turn delivers an output pulse slightly prior to a measured zero current value of the current transformer. The pulse circuit is then connected in series with a fault sensing device which upon occurrence of a fault allows the pulse when created to operate a switching means which in turn connects a charged capacitor to the operating winding of the contact device. Hence, the operating winding is energized immediately prior to the iirst zero current value after the occurrence of a fault.

Accordingly, another object of my invention is to provide a tripcircuit for connecting a capacitor to the operating winding of my novel contacting device only immedately prior to a zero current value through the cooperating contacts rregardless of the instantaneous current value at which a signal is given to operate the contacts at a disengaged position.

Another object of my invention is to provide a trip circuit which measures the circuit current to deliver a pulse slightly prior to a zero current value which pulse is connected to a switching means which in turn connects the charged capacitor to the operating winding to thereby operate the contacting device only prior to a zero current value rregardless of the current value at which the signal to operate the contact device takes place.

All of the preceding objects and many others will become apparent when taken in conjunction with the description in which:

FIGURE 1 shows a cross-sectional view of one embodiment of my novel invention.

FIGURE la shows my invention in a schematic form to more specifically illustrate the principles of its operation.

FIGURE 2 shows a view taken across the lines 2--2 of FIGURE l.

FIGURE 3 shows a view taken across the lines 3-3 of FIGURE 1.

FIGURE 4 shows a second embodiment which may be assumed by the novel unitary movable contact and short circuited winding of my novel invention.

FIGURE 5 shows a top view of the novel contact of FIGURE 4.

FIGURE 6 shows a View taken along the lines 6-6 of FIGURE l to specically illustrate the manner in which the stationary contact may be fastened to the input current conductors and still be able to withdraw the stationary contact subsequent to contact disengagement.

FIGURE 7 shows an embodiment of a stationary contact structure which differs from that seen in FIGURE l.

FIGURE 8 shows another embodiment of my novel invention.

FIGURE 9 shows an embodiment of a structure which may be used to support an operating winding.

FIGURE 10 shows a tripping circuit which in accordance with my novel invention may be used to energize an operating winding only at a time immediately prior to a zero passage of current through the cooperating contacts.

FIGURE 11 shows a schematic illustration of my novel invention wherein a pair of stationary contacts are bridged by a movable contact and a center tapped condenser is connected to distribute the recovery voltage equally on both breaks of the bridging contact arrangement.

FIGURE l2 shows a still further object of my invention.

FIGURE 12a shows a viewof the contact structure of the embodiment of FIGURE l2.

FIGURE 13 shows a schematic view of one application of the embodiment of FIGURE l2.

FIGURE 14 shows a schematic view of another application of the embodiment of FIGURE l2.

FIGURES 15a, 15b and 15C show current time characteristics for the operation of the circuit of FIGURE 13.

FIGURE 16 shows a graphical representation of the operation of my novel device.

The basic principle of my novel invention may be more thoroughly understood with reference to the schematic drawings of FIGURE la. FIGURE la shows a source of electrical energy 2@ as being connected in series with a load 21 and a contact device indicated generally at 22. The contacting device is comprised of a pair of stationary contacts 23 and 24 which are schematically shown as being bridged by a movable contact 25' which, as well as being the movable contact, comprises a short circuited winding.

A second winding or operating winding 26 is positioned with respect to the coil 25 in such a manner that energization of the coil 26 will induce a current in the coil 25 and their mutual magnetic fields will be in such a direction as to drive the coil 25 away from the coil 26 and out of engagement with the stationary contacts 23 and 24.

The operating coil 26 is further shown as being connected in series with a capacitor 27 which is maintained in a charged condition by the D.C. source 2S. A switching means 29 is then provided to selectively connect the chargedcapacitor 27 in series with the coil 26 at any desired time. The switching means 29 may, if desired, be operated responsive to a predetermined electrical condition and the circuit supplied by the energy source 2t), and as will be shown hereinafter, may be further constructed as to discharge the capacitor 27 through coil 26 only immediately prior to a zero current value through the contact structure 22.

One possible embodiment of a contacting device which will operate in accordance with the principle set forth in conjunction with FIGURE la is shown in FIGURES 1, 2 and 3. More specifically, FIGURES l and 2 specifically show a pair of relatively stationary contacts or side conductors 3d and 31 which are biased into Contact engagement with the movable ring contact 32 by means of the Ibiasing springs 33 and 34, respectively. As will be describedmore fully hereinafter, the side conductors 3d and .31..are so constructed as to be withdrawable to a disengaged position responsive tomovement of the movable ring Contact 3210 a disengaged position.

It is seen in FIGURES 1 and 2 that the moving ring contact 32 has the shape of a flat disc and is guided by a cylindrical rod 35. The ring Contact 32 may be constructed of a hard aluminum material with silver plated Contact surfaces on its circumference. The edges of all the contact surfaces are well rounded in order to prevent spark over between sharp points of the movable contact and the stationary contact. As is seen more specically with respect to FIGURE 2, the side contacts 3@ and 3l are constructed to have rounded portions so that they may t closely upon the cylindrical part of the ring and provide a substantially large contact area.

The side conductors 3@ and 3l. may be made of a bronze material with silver plated contact surfaces for cooperation with the contact ring 52. Since the side contacts Sil and 3l are to be movable out of the area of contact engagement with respect to the ring contact 32, these side conductors are connected to the outer conductors 36 and 37, respectively, by means of the identical brush arrangements shown generally as brush assemblies .33 and 3Q, respectively, in FIGURE l.

This brush arrangement which may be specically seen in Conjunction with FIGURE 6 is comprised of a plurality of brush members 4@ which are biased into engagement with the side conductors 3d and 3l by means of the springs 41 which also maintain the brush member 4@ in the groove 42 of the conductor 36 and the groove 43 of the conductor 37.

It is to be noted that the conductors 36 and 37 may be so constructed as to complete a generally air-tight housing around the various components of the contact device. In this case, it would then be possible to operate the device under a high gas pressure whereby the dielectric strength between separating contacts would be increased. This generally air-tight structure `is shown as comprising cylinder 43, hollow member 44, hollow member 45, the conductors 36 and 37 and the base member 46. Hollow members 44 and 4S are of insulating material to thereby electrically insulate side conductors 30 and 3l. The air is further prevented'from escaping from between the side conductor 30 and the conductor member 36 by means Iof the gasket 47 and similarly a gasket 4S is provided to prevent air escape between the side conductor 31 and the conductor member 37.

The operating coil of the winding which is operative to cause motion of the movable contact ring 32 is seen in FIGURES l and 3 as comprising the spirally wound winding 49 which is embedded in a supporting insulating material shown as the cross-hatched portions 50. The operating winding assembly is then positioned on top of a block of insulating material l and a cap of insulating material 52 is then bolted by means of the bolts 53 and S4 in such.

a manner asA to securely maintain the spiral winding 49 on top of the insulating block 51. The top of the cap 52 may then be used as a seat for the contact member 32 when.

it is in the normally engaged position andfurther provide for an accurately controlled minimum separation betweeny the contact ring winding 32 and the spirally wound operating winding 49.

FIGURE 3 specifically indicates the manner in whichv the leads of the spirally wound operating winding@ are taken out of the air-tight enclosure housing the contracting,

device. That is to say, the leads may be taken out through the common tube 55 which is taken through a gasket Se;

and the air-tight seal shown generally at 5'7 lis .beingmainf tained to the housing 43 and 46 by means ofthe bolts 58. This allows the leads to be positionednext to.

Y realized that an equal and 'opposite effect will be imparted4 to the operating winding assembly 11.

By providing the springs dit and 6l, this shock or impulse is more easily absorbed without breakage of any of the associated cornponents.

Pneumatic cushioning is also provided for shock-absorbing purposes since the air in the space 4between the operating winding support 51 and the bottom. member 46 is compressed. This compressed air may then be slowly eX- hausted through the ports 62 and 63 at the sides of the` structure 51. V

It is now understood, in view of the discussion of the operation of FIGURE la, that ,when the operating coil 49 of FIGURES l and 3 is energized, as by the discharge of a capacitor, an extremely high cunrent. will be induced. in,

the ring 32 and this ring will be driven away fromthe spiral winding 49 to a disengaged position with respect to the side contacts 3l) and 31. It is, however, necessary to provide a means to absorb the energy of the ring contact 32 once the contact disengagement .has been effected.

rThis energy absorbing means is shown in FIGURES l andv 3 as the cylinder 43.

More specically, the cylinder ,431has an internal cross-` sectional area which .will cooperate with the yshape of the movable contact 32. Hence, in the case of the contact 32 which has a substantially circular shape, the internal cross-sectional area of the walls o4 of the cylinder 43 will have a corresponding circular shape.

Therefore, when the ring contact 32 is driven away from the operating winding 49 by their mutual magnetic fields, the ring Contact 32 `willenter theV cylinder 43 and compress the air, which may already be in a highly compressed state, between the top surface of the movable contact 32 and the enclosed portion 65 of the cylinder 43. In View of this compression, a force will develop tending to retard the motion of the movable contact 32. That is to say, the kinetic energy of the ring contact 32 will be,

transferred to the compressed gas within the cylinder 43.

When, however, a complete transference of energy takes place, it is seen that the ring contact 32 will now be driven back towards the position of contact engagement by means of the compressed air within the cylinder. In order to avoid this, an angular depression of recess 66 isprovided within the cylinder wall o4 so that upon passing the angular depression 6e, a port will be formed between the depression 6o and the movable contact 32 to allow the escape of compressed air between the movablecontact 32 and the enclosed end 65 of the cylinder 43. Inview of this exhaust of the gas, which is at a higher pressure than the gas at the bottom of contact 32, it is seen that a great deal of the rebound force will be exhausted. Upon con-` tinued travel past the angular depression 66 and toward the enclosed end 65, the remainder of the kinetic energy of the movable contact 32 will be exhausted in a further but much smaller compression of the air captured between the contact 32 and the enclosed end of the cylinder 43.

In view of this slighter compression of air, the ring contact 32 will be brought to a standstill and eventually thrown back to pass the angular depression 66 with substantially the same velocity with which it had passed it in the opposite direction. After passing the port 66, however, it isto be realized that'a decompression will take place within the cylinder 43 until the contact 32 emerges therefrom. This decompression will serve to decrease the velocity of the ring contact 32 until it subsequently is returned to the original contact engaged position at a very low velocity.

If desired, the angular depression 66 could have been replaced by a valve means whereby air is allowed to escape or is brought into another section of the apparatus. In this case, as is true of the previously described case, it would be possible to absorb the complete kinetic energy of the movable contact 32 and to thereafter latch it or maintain it in a disengaged position when it reaches a predetermined distance of separati-on from the cooperating contacts and 31. p

I'f, however, the contact 32 is allowed to return to its original position as has been described in conjunction with the structure shown in FIGURES 1, 2 and 3, it would be extremely undesirable to allow Contact engagement to reoccur between the contacts 30 and 31 since this would reestablish the disengaged circuit.

If this is to be avoided and if the contact 32 is not to be latched or maintained in a disengaged position, I propose to so construct the side conductors 30 and 31 that they are moved or withdrawn to a remote position responsive to the motion'of the contact 32.

In FIGURE 1, compressed air supplies 67 and 68 are schematically lshown as being connected to the ports 69, 70, and 71, 72 respectively. It is to be noted that the channel 70 will lead compressed air into the space 73 between the side of the conductor 36 and the pist-on 74 of the side conductor 30 and similarly, the channel 72 will lead compressed air into the space 74a which llies between the wall of the conductor 37 and the piston 75 of the side conductor 31. If, therefore, the valves shown schematically as valves 76 and 77 of compressed air supplies 67 and 68, respectively, are operated simultaneously with the energization of the coil 49 for moving the movable contact 32 to a disengaged position, then it is seen that compressed air will ilow into the openings 73 and 74a to thereby drive the pistons 74 and 75 in a direction away from the area of contact engagement with the contact 32. By providing the gaskets 78 and 79 for the side conductor 30 and the gaskets 80 and 81 for the side conductor 31, it is seen that this compressed air which is used to drive the side conductors 30 and 31 to a removed position may not escape from between the housing members 82 and portion of 83 of the side conductor 30 and similarly from between the housing member 84 and portion 85 of the side conductor 31.

When it is desired to close the circuit once again, it is only necessary to defeat the compressed air supplies 67 and 68 whereby biasing springs 33 and 34 will move side conductors 30 and 31 back into engagement with the movable contact 32 which rests on insulating cap 52. Closing the circuit breaker by moving the stationary side contacts into engagement withL the movable contact situated in its rest position of the closed breaker permits it to interrupt a short circuit at closing by expelling the movable contact even while the stationary side contacts are still in the closing stroke. Hence, the circuit breaker is trip free. l

It is to be noted that this effect could be similarly obtained in the absence of the compressed air supplies 67 and 68 by leading the air, which would be com- 10 pressed in the cylinder 43 by the motion of the movable conductor 32, to the openings 74a and 73.

It is obvious that many modiications of the components shown in the contact device of FIGURES l, 2 and 3 are possible and come within the scope of my novel invention. By way of example, the movable contact ring 32 of FIGURE 1 could have assumed the shape shown in FIGURES 4 and 5 which show a contact ring 90 having an annular contact 91 and Contact surfaces 93 and 94 which could cooperate with side conductors. Obviously, contact surfaces 93 and 94 could be along any circumferential portion of the ring 90. In the case of the movable contact of FIGURES 4 and 5, it is seen that no sharp edges are provided which would allow ashover between the movable contact and cooperating stationary contacts. Similarly, the cut away portion 91 allows a more rapid increase in separation between the movable contact 90 and its cooperating stationary contact than would a contact having the shape of contact 32 of FIGURE 1. Hence, the rate of rise of tlashover voltage is increased.

The support block 51 of FIGURE 1 which supports the spiral winding 49 could have been constructed as shown in FIGURE 9 of an upper insulating section 95 and a lower section of high density material 96. The two sections 95 and 96 may then be maintained together by a bolt means which serves a dual function by extending through the openings 97 and 98 to fasten a top cap such as the cap 52 of FIGURE 1 which would in turn maintain the spiral winding or operating winding to the insulated block 95 of FIGURE 9. By so providing this additional mass, it is seen that the shock-absorbing properties of the structure are enhanced since a greater mass must be accelerated by the same force. Hence, the acceleration of the composite blocks 95, 96 of FIGURE 9 would be less than that of the block 51 of FIGURE l and stress problems would be reduced accordingly.

The `side conductors 30 and 31 could be modified so that they may operate on an underpressure principle for withdrawal to a remote position after contact disengagement as is shown in FIGURE 7 with reference to side conductor 31. Obvi-ously, side conductor 30 could be constructed in an identical manner. In the case of FIG- URE 7, it is `seen that the space 74a which lies between the conductor 37 and the piston member 75 is, because of the ports 100 and 101, at the same pressure as is the rest of the interior of the contacting device. Similarly, the ports 102 and 103 allow the space containing the Spring 34 to be under the same pressure as is the rest of the apparatus. This is clearly distinguished from the case of FIGURE 1 in which the space 74a was, in view of the gaskets 48 and 80, at a much lower pressure than was the rest of the apparatus.

In the case of FIGURE 7, however, it is seen that the space defined by the end portion 84 of the side conductor 31 and the housing member 104 are at a pressure defined by the pressure of the compressed air supply 105 when piston 106 is positioned to bring port 107 into engagement with both passages 108 and 109. Hence, pressure conditions during normal contact engagement in the case of FIGURE 7 will have the side conductor 31 biased into engagement with a movable ring contact by both the spring 34 and the pressure of compressed air supply 105.

Plunger 106 is movable within the cylinder 110 by means of a coil 111 when the coil is energized by an electrical voltage source 112. A relay shown generally at 113 is then provided to have a coil 114 and a pair of contacts seen generally at 115 which are engaged to thereby connect the voltage source 112 to the coil 111 upon energization of the coil 114 from the terminals 1'16. Upon contact engagement of the contacts 115, the coil 111 is energized and the plunger 106 will be rapidly moved to the right to thereby bring the port 107 out of registry with the air passage 108 and allow the air passage 108 access to the open end 117 of the cylinder 1'10. IUnder this condition, it is seen l 1 thatthe pressure upon the end 84 of the side conductor 31 is substantiallyv reduced and the pressure in the volume 74a which is at the relatively high pressure under which the system operates is then suicient to drive the complete assembly away from the area of contact engagement.

If, therefore, the terminals 116 are electrically connected to be energized responsive to the same electrical conditions which actuate the energization of the operating winding, such as the operating winding of FIGURE 1, then it isr clearly seenthat the side conductor 31 will be moved away from the area of contact engagement at the same time that contact disengagement takes place. Hence, upon subsequentv return of the movable Contact to its original position, a re-engagement of the contacts will not occur.

|FIGURE 8 illustrates a second embodiment which could be taken by the circuit interrupting device of. FIGURE 1. Inthe case of FIGURE 8, however, the movable ring contact 120 completes an electrical path between current carrying side conductors I121 and 124 which may be constructed in the same manner as was side conductor 31 of FIGURE 1, and the contact post 122 which conducts the current to a terminal 123. Side conductors 121 and 124 may be part of an arrangement of radial side conductors forming a pattern similar to the one shown in iFIGURE 6 carrying current radially over the whole ring.

The current carrying member 122 is further provided with a recess portion 125 which acts as did the cylinder 43 in the case of FIGURE y1 to absorb the kinetic energy of the movable contact 120. If desired, the recess 125 may be provided with an angular depression which will act in the same manner as did the angular depression 66 of FIGURE 1 in order to allow the movable contact 12) t0 return to its original position'at substantially a zero velocity. FIGURE 8 further shows a spiral wound operating winding 126 which in this case is shown as being embedded in a material such as an epoxy resin.

The epoxy resin support 127 further encloses the leads 139 and 131 ofthe spiral winding 126 out of the support member 1.27.

Itis further seen in FIGURE 8 that the lead 131 comes. directly out to the terminal 132 while the lead 13t3lwhich is terminating at the terminal 133 is interrupted by the air gap shown generally at134. yWithin the air gap 134 and connected to terminal 135 is disposed an auxiliary electrode 136 which is so constructed that when a sufficient potential -is impressed between the terminals 133 and 135 a flash over will occur between the electrodes 136 and 137 to thereby ionize the air within the air gap 134.

Upon this ionization, it is seen that theelectrode 138 0f the conductor 13@ and theelectrode 137 of the conductor 136 are electrically connected by virtue ofthe ionized air within the air gap 134.

Therefore, if a charged condenser is connected across the terminals 132 and `133 and the signal to initiate contact disengagement between the contacts 121) and 121 of FIG URE 8 is impressed across the terminals 133 and 135,v then upon this signal, the air gap 134 will be broken down and the charged condenser will be allowed to discharge into the winding `126 to thereby effect contact disengagement.

It has been previously mentioned that in order for my novel high speed contact device to work effectively, that the instantaneous breakdown voltage between the separating contacts must be greater than the instantaneous recovery voltage at all times. By placing a condenser across the separating contact, the rate of rise of the recovery voltage will be decreased. In the case` of va Contact device having a pair `of stationary contacts which are bridged by a movable contact, 4I have found that by utilizing a center tapped condenser and connecting the condenser across the stationary contacts and connecting the center tap to the movable contact I can equally distribute the recovery voltage across each break,

`If this were not the case, it would then be possible that the recovery voltage would not be equally distributed and in theV insulators 143 and 144. The movable Acontact 145 is then shown as being guided on a conductive guide post 146 which is in turn connected to the center tap 147 of the condenser 140. By so forming this connection, I can now assure that the instantaneous recovery` voltage between the side contact `141 and the movable contact 145 and the side contact 142 and the movable contact 145 will be equally distributed. Similarly, the capacitor, when so connected, will tend to smooth the higher harmonics of the.

recovery voltage which are primarily responsible. for the high rate of increase of this recovery voltage.

`It has been previously mentioned that a tripping circuit would be desirable such that Contact disengagement occurs slightly prior to a zero current value. FIGURE 10 presents a novel circuit that will accomplish this end whereinthe capacitor 150 serves to discharge through an operating. winding 151 to thereby impart a repelling force to the uni-V tary contact and coil 152 which connects the stationary.

contacts shown schematically as 153 and 154.

In FIGURE 10 it is seen that the opening coil 151 could correspond to operating coil 49 of :FIGURE 1, the movable contact 152 could correspond to the movable Contact 32 of FIGURE l, and that the stationary contacts 153 and 154 correspond to the side conductors 30 and 31l of `FIGURE i1.

Conductor 155 schematically represents a portion of a cincuit which is being protected by the contact deviceA includingthe contacts. 152, 153 and 154. The instantane. ous current in the conductor 155 is measured by a highA quality current transformer 156, the output of which is impressed on a irst circuit including the `capacitor 157, winding 158 and a second circuit comprising a capacitor 159, resistor 160 and inductor 161. The current throughthe coil 158 is forced, by proper circuit design ofthe components 157 through 161, to lead the current measured at thev output of vthe current transformer 156. The amount of this advance will, as will be seen hereinafter, determine the .pretripping time or the amount of time prior to ther passage of .a zero current value at which the contact 152-will disengage the stationary contacts 153 and 154 of FIGURE 10.

Winding 158 is Ythe. input winding of a transductor 162 which may have a core of highly saturable type material. The transductor 162 is more specifically constructed to include a D.C. pre-excitation circuit, including the winding 163, D.C. source 164 and adjustable resistor 165 suchV that a voltage pulse will be. generated in the sec-4 ondary winding 166 when the primary current approaches a zero value.

In the event that the circuit protecting device, by wayv of example, is being utilized for` over-current protection, then an overcurrent relay 167 is provided as is shown in. FIGURE 10 to be normally open andV to close upon the occurrence of a fault condition. Hence, upon the occurrence of a fault, the relay contact 167 closes and the next pulse produced in the winding 166 will reach the grid of the tube 168 to thereby make this tube conductive. The capacitor 169. which is normally charged by the D.C. source 170 thus discharges through the primary winding 171 of the khigh voltage air transformer 172. In view of voltage across the primary winding 172, a high voltage is impressed across the secondary winding 173 of the trans-V former 17.2 to thereby cause the tubes 174 and 175 to flash over. It is to benotedthat the high voltage on the winding 173 will be at a very high frequency .to 'thereby make the timedifference of .discharge of the tubes 174 and 175 negligible.

Upon flash, over of the, tube 174,- the ,Capacitor k15() which is maintained in a charged condition by means of a D.C. source, including the transformer 177 and the rectifiers 178 through 181, may now discharge itself through the operating winding or drive coil 151 to thereby effect contact disengagement between the movable contact 152 and the stationary contacts 153 and 154. Resistor 176 is provided in order to dampen and extinguish the high frequency oscillations produced inthe discharge ofthe capaci-tor 150.

It is. to be specifically noted that the discharge of capacitor 150 to effect contact disengagement or motion of the movable contact 152 is eected only upon the delivery of a pulse from winding 166 after the closure of the contact 167, this pulse occurring immediately prior to the occurrence'ot' a zero current value in the conductor 1,55. Hence, any arc that is formed upon contact separation will be extinguished upon passage of the current through its zero value.

FIGURE l2 shows an embodiment of my novel contacting devic'evwherein the guide member serves as the stationary contacts of the system. FIGURE 12 more specifically shows an operating coil 200 through which a strong oscillatory capacitor discharge current may flow. A closed ring 201 serves as the secondary coil of a transformerhaving the primary coil 200 and, as in the previous embodiments, is repelled by the strong short circuit forces developed between the currents flowing in the coil 200 and the ring201. Operating coil 200 is supplied with this current by means of the leads 202 and 203 which are connected to an energizing circuit. The movable contact 201 is then seen as cooperating with stationary contacts 204, 205. Contacts 204 and 205 as seen in FIGURES 12 and 12a are split into three parts by three slots and have a hole inside which makes them elastic in the r-adial direction in suchpa way as to make good positive contact to the movable Contact 201. Hence, when the contacts are closed, the movable ring 201 is tightly jammed upon the outer cone of the contact 204 and makes good contact with the iixed contact 205 which is elastic and 'compressed radially by the ring 201. A current than can flow freely between the contacts 204 and 205 through the bridging contact 201.

Operating winding 200 of FIGURE 12 is more specifically shown as being embedded in the potted compound body 206 which could be made from an epoxy resin filled with chopped fiberglass or a similar strong filler. This potted compound furthe-r contains the retaining rings 207 and 208. v Rings 207 and 208 may be made of stainless steel to add to the strength of the body and may be slotted to prevent their forming a short circuit winding of their own.

` Cylinder 208 is bolted to the upper electrode 205 by means of the bolts 212, and contact 201 is disposed to travelinto cylinder 209 at great velocity when operating winding 200 is energized. When the movable contalct 201 disappears completely in the cylinder 209, there will be an open gap between the electrodes204 and 205 and a circuit is opened. When the movable contact 201 travels inside of cylinder 209, it compresses air in the cylinder vwhich can escape only with difficulty around the rim of the movable contact 201. At the end of its upward stroke, the movable piece 201 hits the reset piece 210 with a much reduced shock because the compressed air has absorbed most of its kinetic energy which appears as heat in the surrounding air.

The moving ring 201 is then held in the uppermost position bythe expandingspring action of the upper electrode-205. Themovable contact 1 can then be reset to'its original positionby, lowering the reset piece 210a of the-reset piece. 210.

The contact device of FIGURE 12 is seen as applied to acircuit in FIGURE 13 and the operating is graphicallyv shown in FIGURE 15. Magnetic cores 213 and 214 are lodgedaround the conductor 204 which is a portion tor 228 will be discharged.

14 of the circuit being protected. They are-made of a'typ'e of easily saturable magnetic material wound in form of a toroidal core. Cores 213 and 214 are supplied with the bias windings 215 and 216 which are energized from the D.C. source 217 over a choke 218.

FIGURE 15a shows the current fiowing through conductor 204 as i204. The equivalent value of the bias current is coil 215 is shown as i215, and the equivalent bias curren-t in coil 216 is shown as i216.

Considering the core 213, the bias current i215 and the main current i204 compensate each other at the time t-1, which causes this core 213 to unsaturate and a current pulse is now transformed into the output coil 219 as shown in FIGURE 15b. If the current i204 is smaller than the bias current flowing into the coils y215 and 216, this transformation does not occur and no voltage is induced in the windings 219 or 220. The output of coils 219 and 220 is rectified in the rectifiers 221 and 222 and negative voltage pulses like the one produced in the interval time of the time 1 1, t-2 of FIGURE 15b do not pass and therefore no voltage appears on the resistor 223.

Circuit connections are thus provided such that the output of the rectifiers 221 and 222 appears on the electrodes 224 and 225, respectively. The electrodes 224 and 225 are further constructed to be positioned in a radioactive gaseous medium as described in co-pending applicaton Serial No. 558,348, filed January 10, 1956, now Patent Number 2,971,130, granted February 7, 1961, and assignee of the instant application. A high voltage appearing on either of these electrodes will flash them over to the electrode 226, which then can also draw an arc from the electrode 227. The electrodes 226 and 227 are kept at a high voltage by the capacitor 228 which is charged by an auxiliary trickle charger which is not shown in FIGURE 13.

It is, therefore, seen that when the current i204 is larger than the bias current as shown in FIGURE 15a, a positive voltage pulse is induced in winding 219 between the time interval I-3 and t-4 as shown in FIGURE 15b. This will cause the gap 226e227 to flash over and discharge capacitor 228 through the operating winding 200.

Current pulses which are induced in the negative direction are shown in dotted lines in FIGURES 15b and' 15C. Only the positive current pulses as shown by the solid line between t-3 and t-4 of FIGURE 15b and t-7` and t-S of FIGURE 15C can flow through the rectifiers 221 and 222. The resistor 223 permits the reverse current of these rectifier-s to flow and prevents voltage from appearing on the electrodes 224 and 225 during the negative half cycle. n

By adequately choosing the magnitude of the bias current, it is seen that it is possible to initiate contact interruption by advancing the current pulses in such a way that at the time the current goes through zero, the capaci- If the contact interrupts a short time before the current goes through zero, a small arc is formed in an extremely strong magnetic held which makes this arc rotate very rapidly around the vertical axis of the circuit breaker. This arc then is burning between cold electrodes and its current goes through Zero almost immediateiy after the arc is formed to quench the arc and prevent further burning.

FIGURE 14 shows afurther application of the embodiment of FIGURE 12. A heavy current induction coil 230 having an air core mutual induction coil 231 with many turns is connected in series with the contacts 204 and 205. If the rate of rise of current in the coil 230 suddenly assumes a very high value, a high voltage pulse is induced in coil 231 causing an arc between the electrodes 232 and 223. This, in turn, causes an arc between the electrodes 233 and 234 discharging the capacitor 235 into the coil 200 which then opens the contact between the electrodes 204 and 205 by displacing the sliding contact 201 upwardly. The circuit is now..

arraoio closed through the fuse 236 `which is a relatvely low currentfuse and which blows almostinstantaneously. During the time which the fuse 236 needs4 to interrupt, the contact 201 has travelled far enough upward to prevent any arc to form. Hence, circuit interruption is achieved.

without arcing between the main contacts 201, 204 Yand 205 and in theabsence of special circuits to assure current interruptionimmediately prior. to a zero current value.

' The principle of operation ofv my novel device may be more fully vunderstood with reference to FIGURE 16 and FIGURE 1. The travel-time curve of a device as shown in FIGURE 1 follows an equation:

where u, B, and 'y are constants depending on the particular structureinvolved. Hence, the travel of the movable coil and contact structure occurs very sluggishly atV first, but it at a very high rate once it starts moving. Accordingly, itis essential that the contacts remain in en* gagementas long as the travel is slow and are separated only when the contact moves at high speed.

FIGURE 16 shows thev operation of the embodiment of FIGURE l. From the moment a current is initiatedl in coil 30 until the movable Contact 32 has moved upwards,vfar enough tov be entirely disengaged from the fixed contacts 3i) and 31, there is a ltime delay of 160 microseconds (0.000160 second). locity of the contact is 80 meters per second Accordingly,` when the contacts separate, the ashfover distance increases rapidly which means that the Hash-over voltage increases withV about the same rate. therecovery voltage, which rises less rapidly than the flash-over voltage, is unable to flash-over the opening circuit breaker.

A major drawback of the system described previously is the poor. efiiciency of the drive. Energy stored inthe capacitor is released toY become magnetic field energy in the `drive coil. Magnetic field energy effects displacement of coils, causing decrease of field energy and increase of kinetic energy of the moving bodies. Due to the inherent geometry of the air coils, the energy transferred tol kinetic form is relatively small andthe major part of the energy oscillates between capacitor and variable inductor causing variable frequency oscillation which is a loss for the system. Practically attainable efficiencyy is on'` the orderofl to 5 percent (ratio of kinetic energy to capacitor. energy) and this low efficiency has several drawbacks:

(l) Highpenergy capacitors are expensive andlbulky.

(2) Waste magnetic energy tends to explode coils.

(3) Tripping circuits must handle Waste energy.

(4) Short relative'motion uncouples coils which makes the system ineffective after a short travel.

Bolt 35 in FIGURES 1, 2 and 3 and bolt- 146m FIG- URE 1l may be made from a ferrite, i.e., a ferromagnetic ceramic material of the form XFeaO4 where X stands for a metal such as manganese, iron, copper, nickel, cobalt, magnesium, lithium, etc. Multiple ferrites are known to have very high permeability (of the Order of 1000)y anda resistivity several billion `times higher than ordinary magnetic materials. A center post madev of such a material or a bolt surrounded by a sleeve of such a materialwill carry a high densityand high frequency magnetic flux to effect a magnetically close coupling betweenl the drive coiland the driven coil. In View of .the highpermeability of this material, the magnetic energy contained in the initial magnetic field will be extremely low, causing an extremely steep and high rate of increase of the. driving current. This in turn causes a rapidly increasing relative motionl of the coils. By virtue of the magnetic core in the coils the coupling between them remains high in spite of the increasing distance, effecting a repelling action over a much larger period of time and distance as obtainable without the magnetic core.

At this time the ve-V For this reason In the foregoing the invention has been described;-

solely in connectionwith specific illustative.embodiments thereof. Since many yvariations and. modifications of .the invention will now be obvioustothose skilledin the'ar't, I prefer to be bound notby the specific disclosures herein?.`

contained but only by the appendedfclaims..

I claim:

1. A protective circuit for a contact device; said con.

tact device comprising a pair offcooperable contacts'relativelymovable into and out of engagement withy one an. other; a irstwinding and energizing means for saidfirst winding; one of saidk cooperable contacts being a second winding; said second lwinding being positioned to have a current inducedA therein responsive to energization of said first winding; the magnetic fields of saidfiirst and sccondvwindings being in a direction to repelone another to thereby effect relative motion between said pair ofv cooperable contacts; said protective circuit including energizing means for energizing said first winding; said energizing means including means responsiveft'o the current through said cooperable contacts; said energizing means energizing said first winding at a predetermined time prior to an instantaneous zero current value for the current through said cooperable contacts; said energizing means including magnetic means magnetically coupied to said circuitthrough'said cooperablecontactsi* said energizing means including magnetic means magnetically Vcoupled to said circuit through said coopera# ble contacts, a capacitor, and a switching means; said capacitor being normally charged; said switching means..

being connected in circuit relation with respect to said. capacitor to normally prevent discharge'of said capacitor; said switchingl means being operabley to a closedj pos'i tion to permit discharge of said capacitor; circuit con-v nections for transmitting the energydischarged by said capacitor to said first winding; ,said'switching means being coupled to said magnetic means and being opfer-rv ated to said closed position -at saidv predetermined time,

2. A protectivefcircuit forV a contacting device conn prising a `movablecontact and a con'iplementaryV contact engageableby said movablecontact; saidy movablecontact bein-g formed of a conductive electrically energiz'able winding generating a magnetic iield when energized and means positioned'for generating a magnetic iield for repelling said first mentioned Vmagnetic iield; and energizing means for energizing saidrst winding; said protectivecircuit including energizing means 'including means responsiveV to the current through said cooperable contacts; said energizing means energizing said first winding at a predetermined time prior to an instantaneous zero current Value for the current through said cooperati-4 ble contacts; said energizing means'including magnetic means magnetically coupled to said circuit through sald .cooperable contacts, a capacitor, and a switching means; saidv capacitor being .normally charged; said switching means being connected in circuit relation with respect to said capacitor to normally prevent dischtirge of said capacitor; said switching means being operable to a closed position to permit discharge of said capacitor; circuit connections for transmitting the energy discharged by said capacitor to said first winding; said switchi-.

ble contact structure movable between an engaged and disengaged position with respect to said stationary contact structure; at least a portion of said movable contact structure forming a current carrying path with at least a portion of said stationary contact structure; at least a portion of said movable contact structure delining a short circuited winding; said operating circuit including an energizing winding positioned immediately adjacent said short circuited winding when said movable contact structure is in said engaged position and means for energizing said energizing winding; said means for energizing said energizing winding including means responsive to current through said current path; a source of energy normally disconnected from said energizing winding and connecting means operable to connect said energy source to said energizing winding; said means responsive to current through said current path being connected to said means operable to connect said energy source to said energizing winding and delivering an operating signal thereto under predetermined conditions; said means operable to connect said energizing winding being operable only prior to zero instantaneous current through said current path.

4. A protective circuit for an electrodynamic circuit interrupter; said electrodynamic circuit breaker cornprising a stationary contact structure and a movable contact structure movable between an engaged and disengaged position with respect to said stationary contact structure; at least a portion of said movable contact structure forming a current carrying path with at least a portion of said stationary Contact structure; at least a portion of said movable contact structure defining a short circuited winding; said energizing means including an energizing winding positioned immediately adjacent said short circuited winding when said movable contact structure is in said engaged position; said protective circuit including means for energizing said energizing winding; said means for energizing said energizing winding including means responsive to current through said current path; a source of energy normally disconnected from said energizing winding and connecting means operable to connect said energy source to said energizing winding; said means responsive to current through said current path being connected to said means operable to connect said energy source to said energizing winding and delivering an operating signal thereto under predetermined conditions; said means operable to connect said energizing winding being operable only prior to zero instantaneous current through said current path; said means operable to connect said energy source to said energizing winding including a normally charged capacitor and a switching means connected in discharge controlling relation with respect to said capacitor; said switching means being conditioned to operate to a closed condition responsive to signals derived from said means responsive to current through said current path at any instant and being closed after receiving said signals at a time prior to said zero instantaneous current.

5. In a contacting device for an electrical circuit; a capacitor, means to maintain said capacitor in a charged condition, a switching means, an operating winding and a pair of cooperable contacts; said cooperable contacts being constructed to be moved to a disengaged position responsive to the discharge of said charged capacitor through said operating winding; said capacitor being connected to said operating winding responsive to operation of said switching means to thereby discharge through said operating winding; a current transformer; fault sensing means and means to advance the phase of the output current of said current transformer; said current transformer being connected to continuously measure the current flowing in said electrical circuit; said fault sensing means being operable responsive t0 occurrence of a predetermined condition in said electrical circuit; circuit connections for connecting the output current of advanced phase to a transductor means whereby an output pulse is produced at a time prior to zero current in said electrical circuit corresponding to the advanced phase of the output current of said phase advancing means; said switching means being constructed to conneet said capacitor to said operating winding responsive to energization by said output pulse of said transductor means; said fault sensing means being constructed to complete circuit connections between said transductor means and said switching means responsive to the occurrence of said predetermined condition in said electrical circuit to thereby allow the output pulse of said transductor means to operate said switching means at a time immediately prior to the occurrence of a zero current value in said electrical circuit following the occurrence of said predetermined condition.

References Cited in the file of this patent UNITED STATES PATENTS 1,287,231 Chubb Dec. 10, 1918 1,827,940 Greenwood Oct. 20, 1931 2,261,686 Kesselring Nov. 4, 1941 2,290,683 Gieifers July 21, 1942 2,499,394 Kcsselring Mar. 7, 1950 2,691,128 Wegener Oct. 5, 1954 2,774,920 Kesselring Dec. 18, 1956 2,942,155 Loeler June 21, 1960 2,951,188 Diebold Aug. 30, 1960 2,971,130 Diebold Feb. 7, 1961 FOREIGN PATENTS 422,775 Great Britain Ian. 17, 1935 OTHER REFERENCES The Electric Journal, vol. 34, No. 5, May 1937, pages 193, 194. 

5. IN A CONTACTING DEVICE FOR AN ELECTRICAL CIRCUIT; A CAPACITOR, MEANS TO MAINTAIN SAID CAPACITOR IN A CHARGED CONDITION, A SWITCHING MEANS, AN OPERATING WINDING AND A PAIR OF COOPERABLE CONTACTS; SAID COOPERABLE CONTACTS BEING CONSTRUCTED TO BE MOVED TO A DISENGAGED POSITION RESPONSIVE TO THE DISCHARGE OF SAID CHARGED CAPACITOR THROUGH SAID OPERATING WINDING; SAID CAPACITOR BEING CONNECTED TO SAID OPERATING WINDING RESPONSIVE TO OPERATION OF SAID SWITCHING MEANS TO THEREBY DISCHARGE THROUGH SAID OPERATING WINDING; A CURRENT TRANSFORMER; FAULT SENSING MEANS AND MEANS TO ADVANCE THE PHASE OF THE OUTPUT CURRENT OF SAID CURRENT TRANSFORMER; SAID CURRENT TRANSFORMER BEING CONNECTED TO CONTINUOUSLY MEASURE THE CURRENT FLOWING IN SAID ELECTRICAL CIRCUIT; SAID FAULT SENSING MEANS BEING OPERABLE RESPONSIVE TO OCCURRENCE OF A PREDETERMINED CONDITION IN SAID ELECTRICAL CIRCUIT; CIRCUIT CONNECTIONS FOR CONNECTING THE OUTPUT CURRENT OF ADVANCED PHASE TO A TRANSDUCTOR MEANS WHEREBY AN OUTPUT PULSE IS PRODUCED AT A TIME PRIOR TO ZERO CURRENT IN SAID ELECTRICAL CIRCUIT CORRESPONDING TO ADVANCED PHASE OF THE OUTPUT CURRENT OF SAID PHASE ADVANCING MEANS; SAID SWITCHING MEANS BEING CONSTRUCTED TO CONNECT SAID CAPACITOR TO SAID OPERATING WINDING RESPONSIVE TO ENERGIZATION BY SAID OUTPUT PULSE OF SAID TRANSDUCTOR MEANS; SAID FAULT SENSING MEANS BEING CONSTRUCTED TO COMPLETE CIRCUIT CONNECTIONS BETWEEN SAID TRANSDUCTOR MEANS AND SAID SWITCING MEANS RESPONSIVE TO THE OCCURRENCE OF SAID PREDETERMINED CONDITION IN SAID ELECTRICAL CIRCUIT TO THEREBY ALLOW THE OUTPUT PULSE OF SAID TRANSDUCTOR MEANS TO OPERATE SAID SWITCHING MEANS AT A TIME IMMEDIATELY PRIOR TO THE OCCURRENCE OF A ZERO CURRENT VALUE IN SAID ELECTRICAL CIRCUIT FOLLOWING THE OCCURRENCE OF SAID PREDETERMINED CONDITION. 